The study will enroll approximately 186 participants. The study consists of 4 parts: Single-rising dose (SRD) part (Cohorts 1-6, and 18-22), multiple-rising dose (MRD) part (Cohorts 7-15), Cohort 16 with 2-arm parallel design, and Cohort 17 relative bioavailability and food effect 3 period crossover design. Cohorts 1-12 and 18-19, will have 8 randomized participants, with 6 receiving TAK-071, and 2 receiving matching placebo. Cohorts 20-22 will have 12 randomized participants with 3 receiving TAK-071 placebo+donepezil placebo, 3 receiving TAK-071 placebo+donepezil, and 6 receiving TAK-071+donepezil. Cohorts 13-15, will have 6 randomized participants, with 5 receiving TAK-071, and 1 receiving matching placebo. Selected cohorts (Cohorts 10 to 12) will be pretreated for 3 weeks with daily oral doses of donepezil (5 mg QD), followed by continued daily oral donepezil dosing during the TAK-071 treatment period. The planned initial dose of TAK-071 for Cohort 1 is 1 mg and subsequent dose levels to be determined by emerging safety, tolerability, and PK data in preceding cohorts.